1. Field of the Invention
The present invention relates to a head position control device capable of address control of mutually cooperating plural heads thereby enabling faster independent seeking operation of the heads.
2. Description of the Prior Art
FIGS. 1, 2A and 2B show a conventional disk drive mechanism in exploded perspective views.
In FIG. 1 a magnetic disk 1 is supported between a spindle 3 and a cone 2, and said spindle 3 is rotated with a pulley 6 by a drive mechanism consisting of a drive motor 4, a belt 5, a pulley 6 etc. to rotate said disk 1.
A magnetic head 7 for writing and reading information to and from the disk 1 is mounted on a head carriage 8. In response to the direction and amount of rotation of a stepping motor 9, a steel belt 10 moves the head carriage 8 in a direction A or in the opposite direction.
In this manner the head 7 can select an arbitrary track position on the disk 1. Also a shield plate 8a provided on the head carriage 8 and a detecting switch 11 composed of a photocoupler are provided to detect when the head 7 is at a track position "00".
The head 7 is connected to a reading circuit 12 for information reading and a writing circuit 13 for information writing, and the driving motor 4, stepping motor 9, detecting switch 11 etc. are connected to a control circuit 14. FIGS. 2A and 2B are schematic perspective views of the arrangement shown in FIG. 1, however with plural heads 7.
In FIG. 2A there are provided plural magnetic disks 1a, 1b. Mutually cooperating magnetic heads 7a, 7b, mounted on the head carriage 8, are moved by the stepping motor 9 and the reciprocating motion of the steel belt 10. The head 7a is maintained in sliding contact with the disk 1a, while the head 7b is maintained in sliding contact with the disk 1b for mutual information exchange.
In FIG. 2B the disk 1 is provided on both faces (on top and bottom faces) with magnetic layers, and mutually linked magnetic heads 7a, 7b are so positioned as to sandwich said disk 1.
The arrangement shown in FIG. 2B also allows mutual information exchange between plural magnetic heads 7a, 7b.
Since such conventional device is not provided with a function of memorizing the track address of the disk 1, it has been necessary, in shifting the control from one disk to the other in the arrangement shown in FIG. 2A, to store the address in the control system or to effect an additional operation, when shifting the control to the first disk, of returning the head to the track "00" and then making access to a desired track.
The first-mentioned method is shown in more detail in FIG. 3. In the flow chart shown in FIG. 3, steps S1-S4, S51-S53, S6, S7, S81-S83 and S9 are repeated according to the necessity for independent seeking operation of the drives "1" and "2", but the steps S51-S53 and S81-S83 are burdensome to the control system and give rise to a long processing time. On the other hand the second-mentioned method apparently requires a long processing time since the head has to be returned to the reference position or the track "00" before the seeking operation each time the head is switched. In this manner the conventional methods have been associated with drawbacks of requiring a complex and large control system, and of requiring a long processing time in switching the control from one head to the other.